Answer

(b) Lichens can be used as an atmospheric pollution indicator. They do not grow in areas that are polluted, as they are sensitive (especially phycobiont) to oxides of nitrogen and sulphur, hence unable to synthesise organic food and do not grow well. Lepidoptera It is insect order. Lycopersicon It is scientific name of tomato. Lycopodium It is an pteridophyte.

• Lepidoptera: It is an insect order and not used as an atmospheric pollution indicator.
• Lycopersicon: It is the scientific name of tomato and not used as an atmospheric pollution indicator.
• Lycopodium: It is a pteridophyte and not used as an atmospheric pollution indicator.

Answer

(c) The theory of spontaneous generation stated that life can arise from non-living things only. It is also known as abiogenesis.

Louis Pasteur by careful experimentation disapproved this theory and demonstrated that life arose from living forms (pre-existing life).

• (a) The theory of spontaneous generation does not state that life arose from living forms only. This idea aligns more with the concept of biogenesis, which posits that life arises from pre-existing life.

• (b) The theory of spontaneous generation does not claim that life can arise from both living and non-living things. It specifically suggests that life can originate from non-living matter.

• (d) The theory of spontaneous generation does not state that life arises spontaneously, neither from living nor from the non-living. It explicitly asserts that life can emerge from non-living matter.

Answer

(b) These are examples of artificial selection

‘Artificial selection’ is a process in which the breeder choose to perpetuate only those forms that have certain desirable inheritable characteristics.

The other three options are incorrect as mutation is a sudden change in DNA sequence due to mutagenic agents such as chemicals and radiations.

Natural selection is a gradual process by which biological traits become either more or less common in a population as a function of the effect of the changing environment.

Reverse evolution or devolution is a notion that species can change into more primitive forms over time.

• Mutation is a sudden change in DNA sequence due to mutagenic agents such as chemicals and radiations.
• Natural selection is a gradual process by which biological traits become either more or less common in a population as a function of the effect of the changing environment.
• Reverse evolution or devolution is a notion that species can change into more primitive forms over time.

Answer

(c) Palaeontological evidences for evolution refer to the evidences from fossils. Fossils are the preserved remains or traces of organisms from the distant past. The study of fossils is called Palaeontology. The other options are not correct because the development patterns of embryo refer to embryological evidences for evolution.

Homologous and analogous organs provide evidences for comparative anatomy and morphology.

• The development of embryo refers to embryological evidences for evolution, not palaeontological evidences.
• Homologous organs provide evidences for comparative anatomy and morphology, not palaeontological evidences.
• Analogous organs also provide evidences for comparative anatomy and morphology, not palaeontological evidences.

Answer

(b) The bones of forelimbs of whale, bat, cheetah and man are similar in structure, because they have a common ancestor.

These are homologous organs which have different functions across diverse forms, but are developed along same pattern. These organs arise due to divergent evolution.

• (a) One organism has given rise to another: This option is incorrect because it suggests a direct lineage from one organism to another, rather than a shared common ancestor. The similarity in bone structure is due to a common ancestor, not a direct descent from one species to another.

• (c) They perform the same function: This option is incorrect because the forelimbs of whales, bats, cheetahs, and humans perform different functions (swimming, flying, running, and manipulating objects, respectively). The similarity in structure is due to common ancestry, not because they perform the same function.

• (d) They have biochemical similarities: This option is incorrect because biochemical similarities refer to similarities at the molecular level (such as DNA, proteins, etc.), not the structural similarity of bones. The question specifically addresses the structural similarity of the forelimbs, which is due to common ancestry.

Answer

(d) Analogous organs arise due to convergent evolution. These are the organs which have similar functions, but are different in their structural details and origin, e.g., wings of insect and bird.

The other three options are incorrect, because divergent evolution give rise to homologous organs, genetic drift can contribute to speciation and artificial selection is used to produce improved varieties of animals and plants.

• Divergent evolution gives rise to homologous organs.
• Genetic drift can contribute to speciation.
• Artificial selection is used to produce improved varieties of animals and plants.

Answer

$(\boldsymbol{a})(p+q)^{2}=p^{2}+2 p q+q^{2}=1$ represents an equation used in population genetics.

It is a mathematical representation of ‘Hardy-Weinberg principle’. This principle says that allele frequencies in a population are stable and is constant from generation to generation, i.e., the gene pool remains a constant.

• Mendelian genetics: This field focuses on the inheritance patterns of traits as discovered by Gregor Mendel. It deals with the segregation and independent assortment of alleles, but it does not specifically use the equation ((p+q)^{2}=p^{2}+2pq+q^{2}=1), which is a hallmark of population genetics.

• Biometrics: Biometrics involves the statistical analysis of biological data, often for identification purposes (e.g., fingerprint analysis, facial recognition). It does not typically involve the Hardy-Weinberg principle or the equation ((p+q)^{2}=p^{2}+2pq+q^{2}=1).

• Molecular genetics: This field studies the structure and function of genes at a molecular level, including DNA sequencing, gene expression, and genetic mutations. While it may involve allele frequencies, it does not primarily use the Hardy-Weinberg equation, which is more relevant to population genetics.

Answer

(c) Appearance of antibiotic-resistant bacteria is an example of pre-existing variation in the population. When a bacterial population encounters a particular antibiotic, those sensitive to it die.

But some bacteria having mutations become resistant to the antibiotic. Soon, the resistance providing genes become widespread and the entire population becomes resistant.

It is not due to adaptive radiation because adaptive radiation is development of different functional structures from a common ancestral form. Which is also known as divergent evolution.

Transduction is a process whereby, foreign DNA is introduced into another cell via a viral vector.

• It is not due to adaptive radiation because adaptive radiation is the development of different functional structures from a common ancestral form. This process involves the diversification of a species into different forms that are each adaptively specialized to a specific environmental niche.

• It is not due to transduction because transduction is a process whereby foreign DNA is introduced into another cell via a viral vector. This mechanism involves the transfer of genetic material between bacteria through the agency of viruses, not the selection of pre-existing resistant variants.

• It is not due to divergent evolution because divergent evolution refers to the process by which two or more related species become more dissimilar over time, often due to different environmental pressures. This results in the formation of new species from a common ancestor, which is not the case with antibiotic resistance.

Answer

(d) Evolution of life shows that life forms had a trend of moving from water to land. The early vertebrates were fishes (which lived in only water). Some fishes gradually changed into amphibians (can live both on land and in water).

Certain amphibians then transformed into the reptiles (live on land) some of the latter finally evolved into birds (can fly) and than mammals. Thus, showing life forms moved from water to land.

• (a) Land to water: This option is incorrect because the earliest life forms originated in water, not on land. The transition was from aquatic environments to terrestrial ones, not the other way around.

• (b) Dryland to wet land: This option is incorrect because the initial life forms did not start on dry land. The progression was from aquatic environments to land, not from dry land to wet land.

• (c) Freshwater to sea water: This option is incorrect because the earliest life forms are believed to have originated in the ocean. The evolutionary trend was not specifically from freshwater to seawater but rather from aquatic environments (both freshwater and seawater) to terrestrial environments.

Answer

(c) Viviparity is considered to be more evolved because the youngs ones are protected inside the mother’s body and are looked after once they are born, leading to more chances of survival, e.g., mammals.

However, in oviparity, the female lays fertilised/unfertilised eggs covered by a hard calcareous shell in a safe place in the environment. The chances of survival are less as the young ones are left on their own.

• (a) The young ones are left on their own: This is incorrect because leaving the young ones on their own does not provide them with protection or care, reducing their chances of survival compared to being protected inside the mother’s body.

• (b) The young ones are protected by a thick shell: This is incorrect because, although a thick shell provides some protection, it does not offer the same level of care and nourishment that being inside the mother’s body does, leading to lower chances of survival.

• (d) The embryo takes a long time to develop: This is incorrect because the duration of embryo development does not necessarily correlate with the level of protection or care provided to the young ones, which is the key factor in viviparity being more evolved.

Answer

(a) Fossils are generally found in sedimentary rocks, which are formed by the gradual deposition of silt, sand or calcium carbonate over millions of years in regions such as lakes or sea during their formation, the dead animals are carried to the sea or large lake, sink down and get burried in the rocks. The animals, thus preserved in the rocks, are converted into fossils.

• Igneous rocks: Fossils are not typically found in igneous rocks because these rocks are formed from the cooling and solidification of magma or lava. The high temperatures involved in this process would destroy any organic material, preventing the formation of fossils.

• Metamorphic rocks: Fossils are rarely found in metamorphic rocks because these rocks have been subjected to intense heat and pressure, which can alter or destroy the original structures of any fossils that might have been present in the precursor sedimentary rocks.

• Any type of rock: This option is incorrect because fossils are specifically associated with sedimentary rocks. Igneous and metamorphic rocks do not typically preserve fossils due to the extreme conditions under which they form.

Answer

(a) The expected frequency of MN blood group bearings organisms is likely to be $42 \%$. According to Hardy-Weinberg equation, $p^{2}+2 p q+q^{2}=1$

where, $\quad p=$ Frequency of $\mathrm{M}$ alleles,

$p^{2}=$ Frequency of homozygous dominant individuals.

$q=$ frequency of $\mathrm{N}$ alleles

$q^{2}=$ Frequency of homozygous recessive individuals.

$2 P q=$ Frequency of heterozygous individuals

So,

$(0.7)^{2}+(0.3)^{2}+2 p q=1$

$0.49+0.09+2 p q=1$

$\therefore \quad 2 p q=0.42=$ Frequency of heterozygous individuals.

i.e., $42 \%$

• Option (b) $49%$: This option is incorrect because it represents the frequency of homozygous dominant individuals ($M$ allele) calculated as $p^2 = (0.7)^2 = 0.49$ or $49%$, not the frequency of heterozygous individuals ($MN$ blood group).

• Option (c) $9%$: This option is incorrect because it represents the frequency of homozygous recessive individuals ($N$ allele) calculated as $q^2 = (0.3)^2 = 0.09$ or $9%, not the frequency of heterozygous individuals ($MN$ blood group).

• Option (d) $58%$: This option is incorrect because it does not correspond to any of the calculated frequencies using the Hardy-Weinberg equation. The sum of the frequencies of homozygous dominant, homozygous recessive, and heterozygous individuals must equal 1 (or 100%), and $58%$ does not fit into this distribution.

Answer

(b) Directional selection is observed in moth, Biston betularia is industrial melanism. Under this, individuals at one end of the frequency distribution do well light and so more individuals of that type will be present in next generation.

The other options are incorrect because in stabilising selection, average sized individuals are favoured. e.g., weight of new-born babies and in disruptive selection both extremes are favoured, while intermediate varieties are eleminated, e.g., black bellied seed cracker, Pyrenestes ostrinus.

In artificial selection, the individuals with desirable characteristics are deliberately selected to produce a progeny with all those characteristics.

• In stabilising selection, average sized individuals are favoured. e.g., weight of new-born babies.
• In disruptive selection, both extremes are favoured, while intermediate varieties are eliminated, e.g., black bellied seed cracker, Pyrenestes ostrinus.
• In artificial selection, the individuals with desirable characteristics are deliberately selected to produce a progeny with all those characteristics.

Answer

(c) The most accepted line of descent in human evolution is Ramapithecus $\rightarrow$ Homo habilis $\rightarrow$ Homo erectus $\rightarrow$ Homo sapiens.

• Option (a) is incorrect because the sequence places Homo sapiens before Homo habilis, which is not accurate. Homo habilis is an earlier species in the human evolutionary line, preceding Homo sapiens.

• Option (b) is incorrect because it places Homo habilis after Homo erectus. In reality, Homo habilis is considered to have existed before Homo erectus.

• Option (d) is incorrect because it includes Australopithecus and Ramapithecus in the sequence, but places Homo habilis after Homo erectus. The correct sequence should have Homo habilis before Homo erectus.

Answer

(a) Lobe fish is an example for link species.

About 350 mya, fish with stout and strong fins could move on land and go back to water. These were called lobe and they evolved into the first amphibians that lived on both land and water, e.g., coelocanth.

Dodo is an extinct flightless bird. Sea weed is multicellular benthic marine algae chimpanzees are the closest living relatives of humans.

• Dodo bird is an extinct flightless bird.
• Sea weed is multicellular benthic marine algae.
• Chimpanzees are the closest living relatives of humans.

Answer

(b) Darwin is related with evolution by natural selection. According to the theory in the struggle for existence, the individuals which have more favourable variations will survive and reproduce, while others, which have less favourable or unfavourable variations will not puripetuate.

Oparin Put forth abiogenesis theory.

According to abiogenesis Life is originated from the non-living things spontaneously.

Lamarck Use and disuse of organs is one of the important principle of Lamarckism.

Wagner proposed continental drift theory.

It states that part of the Earth’s crust slowly drift atop a liquid core forming different continents. As these continents had different environmental conditions, so plants and animals evolved.

• Option (a) is incorrect:

  • Darwin (1): Darwin is not associated with abiogenesis; he is known for the theory of evolution by natural selection.
  • Oparin (4): Oparin is not related to evolution by natural selection; he proposed the abiogenesis theory.
  • Lamarck (2): This is correct; Lamarck is known for the use and disuse of organs.
  • Wagner (3): This is correct; Wagner proposed the continental drift theory.

• Option (c) is incorrect:

  • Darwin (2): Darwin is not associated with the use and disuse of organs; he is known for the theory of evolution by natural selection.
  • Oparin (4): Oparin is not related to evolution by natural selection; he proposed the abiogenesis theory.
  • Lamarck (3): Lamarck is not associated with the continental drift theory; he is known for the use and disuse of organs.
  • Wagner (1): Wagner is not associated with abiogenesis; he proposed the continental drift theory.

• Option (d) is incorrect:

  • Darwin (4): This is correct; Darwin is known for the theory of evolution by natural selection.
  • Oparin (3): Oparin is not related to the continental drift theory; he proposed the abiogenesis theory.
  • Lamarck (2): This is correct; Lamarck is known for the use and disuse of organs.
  • Wagner (1): Wagner is not associated with abiogenesis; he proposed the continental drift theory.

Answer

(d) The Miller - Urey experiment tested for the occurrence of chemical evolution by stimulating hypothetical conditions present on early earth.

These primitive earth conditions include high temperature, volcanic storms and reducing environment containing methane $\left(CH_{4}\right)$, ammonia $\left(NH_{3}\right)$, hydrogen $\left(H_{2}\right)$ and water $\left(H_{2} O\right)$.

They ultimately found that a large number of simple organic compounds including some amino acids such as alanine, glycine and aspartic acid can be synthesised in into as during chemical origin of life.

• Option (a): Low temperature and an atmosphere rich in oxygen are incorrect because the early Earth had a high temperature and a reducing atmosphere, not an oxygen-rich one. Oxygen-rich conditions would inhibit the formation of organic molecules necessary for the origin of life.

• Option (b): Low temperature is incorrect because the early Earth had a high temperature. While volcanic storms and a reducing atmosphere are correct, the low temperature does not align with the conditions of early Earth.

• Option (c): Non-reducing atmosphere is incorrect because the early Earth had a reducing atmosphere, which is essential for the formation of organic molecules. A non-reducing atmosphere would not support the chemical reactions needed for the origin of life.

Answer

(a) Variations during mutations of meiotic recombinations are random and directionless. Hugo de Vries based on his work on evening primrose stated that it is mutation which causes sudden appearance of variations that results in speciation.

He stated that mutations are sudden, heritable and persistant in successive generation. He contradicted Darwinian variations that are small and directional.

• (b) random and directional: This option is incorrect because mutations during meiotic recombinations are not directional. Directional variations imply a specific trend or direction in which changes occur, which contradicts the nature of mutations that are random and do not follow a specific path or direction.

• (c) random and small: This option is incorrect because while mutations are indeed random, they are not necessarily small. Mutations can vary in magnitude and can sometimes result in significant changes. Hugo de Vries emphasized that mutations can cause sudden and substantial variations.

• (d) random, small and directional: This option is incorrect for two reasons. Firstly, mutations are not necessarily small; they can be large and significant. Secondly, mutations are not directional; they occur randomly without following a specific trend or direction.

Thinking Process Fossils are formed and preserved over times so, all organisms are not equally likely to fossilis. It is based towards organisms with hard parts such as bones of vertebrates or calcareous exoskeleton of invertebrates.

Answer

The organisms with hard parts are likely to be fossilised, than those who do not have such parts. The harder the material, better it would be preserved soft parts fossils occur rarely, e.g., birds and pterosaurs have very light bones, hollowed out and specialised for flight.

So, they have sparser fossil record as compared to mammals, whose bones are partially mineralised during life.

Thinking Process

The geological changes that took place over time transformed many water-bodies into solid rocks and mountains, so fossils of aquatic organism are more likely to be found in mountains.

Answer

Yes, aquatic forms of life do get fossilised, infact, there are more aquatic than terrestrial fossil organisms. Such fossils of sea creatures are found in mountains as opposed to deep sea beds

This is because the rocks in which the fossils are found used to be at the bottom of oceans Due to the changes in the crustal plates over time, the ocean sediments were pushed up to form mountains.

Answer

These terms are used to classify organisms according to their evolutionary history.

Simple organisms refer to those organisms that have simple structural and functional organisation and are considered primitive, whereas Complex organisms refer to those organisms that have higher and complex levels of structural and functional organisation.

These are more advanced and said to have arisen from simple organisms.

Answer

To estimate the age of a living tree, following steps are required

(i) Measure the circumference of the tree trunk (at about 4.5 feet above the ground).

(ii) Calculate the diameter of the trunk. This is done by dividing the circumference by 3.14 . Divide this (i.e., diameter) by 2 to get the radius.

(iii) Determine the growth factor. A tree’s growth factor is the measurement of the width it gains annually. The trees’s growth factor can be seen from the data available or by measuring the rings of a dead tree from the same species.

(iv) Multiply the diameter and the tree species average growth factor and the so done calculating suggest the approximate age of the tree in years.

Answer

When unrelated animals converging to the same form or structure, that is very adaptive in their common environment. It is called convergent evolution, e.g., Australian marsupials and placental mammals.

Such as (placental wolf and Tasmanian wolf). These two sub-classes of mammals have adapted in similar ways to a particular food supply, locomotor skill or climate.

Their resemblances in overall shape, locomotor mode and feeding and foraging are superimposed upon different modes of reproduction, the feature that accurately reflects their distinct evolutionary relationships.

Answer

The age of a fossil can be computed by radioactive dating (also called radiometric dating). It is a technique based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. Among the best known techniques are radiocarbon dating, potassium-argon dating and uranium lead dating.

Answer

Conditions promoting adaptive radiation are much of the diversity of life originated through episodes of adaptive radiation during periods when ecological space became available for diversification. There are two primary mechanisms through which ecological space can become available.

(i) intrinsic changes in organisms

(ii) extrinsic effects, including environmental change and colonisation of isolated landmasses.

Answer

The age of a rock in years is called its absolute age. It is determined by the natural radioactive decay of certain elements, e.g., uranium, when decays turns into lead. The parent atoms of uranium are converted into daughter atoms of lead over a fixed interval of time. This interval is the decay constant.

The ratio of parent-daughter atoms changes in a quantity that can be measured.

The radioactive half-life (the amount of time required for one half of the parent atoms to beonverted to daughter atoms) is used to calculate the age of the rock.

Answer

Functional macromolecules are evolving towards creation of a complex organism. There are various evidences that are common to simple and complex forms of lite indicate common ancestry, e.g., histones protein tend to be well preserved among all eukaryotes, from amoebas to blue whale or to humans, with only one or two amino acids different.

The genetic code is nearly identical for all known life forms, from bacteria to archaea or animals and plants.

Thinking Process

According to Hardy-Weinberg equilibrium, $p^{2}+2 p q+q^{2}=1$.

Answer

The likely frequency of $\mathrm{B}=\mathrm{BB}+1 / 2 \mathrm{Bb}$

$ \begin{aligned} & =\bigl[22+\frac{62}{2} \bigr] \% \\ & =53 \% \\ \text { The likely frequency of } \mathrm{b} & =\mathrm{bb}+1 / 2 \mathrm{Bb} \\ & = \bigl[16+\frac{62}{2} \bigr] \% \\ & =47 \% \end{aligned} $

Answer

The other two factors that affect Hardy-Weinberg equilibrium are mutation and natural selection.

Mutation is a sudden heritable change in an organism which is generally due to change in the base sequence of the nucleic acid in the organism’s genome.

Microbial experiments show that pre-existing advantageous mutations when selected will result in formation of new phenotypes. Over few generations, this would result in speciation. Thus, resulting in changed frequency of genes and alleles.

Natural selection is a phenomenon by which organisms possessing heritable variations enabling their better survival reproduce and leave greater number of progeny than their counterpart.

It can lead to stabilisation (in which more individuals acquire mean character value), directional change (more individuals acquire value other than the mean character value) or disruption (more individuals acquire peripheral character value at both ends of the distribution curve).

Answer

Sometimes, a small number of individuals become isolated from a larger population to form a new population at some distance away from their place of origin.

The gene pool of the new population differs from the source population. It is possible that the change in allele frequency is so drastically different in the new sample that they become a different species. The original drifted population becomes founders and this effect is called founder effect.

Answer

Ramapithecus was more man-like. It walked erect on its hind legs, ate hard nuts and seeds like modern man and had jaws and teeth similar to humans. It arose from Dryopithecus, which was considered to be a common ancestor of man and apes.

Dryopithecus was more ape-like with same length of arms and legs.

Answer

The first hominid was known as Homo habilis. The brain capacities were between $650-800 \mathrm{cc}$. They probably did not eat meat.

Answer

Homo habilis probably did not eat meat. This creature was the first human like being, with brain capacities between 650-800cc.

Short Answer Type Questions

Answer

Yes, we can correct this as life evolves from pre-existent life. The first life that appeared on earth was apparently the result of chemical evolution, i.e., the life originated from inorganic molecules which formed organic molecules, further forming complex compounds.

This finally resulted into simple cells and then simple organisms, wherein complexity development with time. However, once life originated, abiogenesis could not follow, and hence, life evolved further only through biogenesis, i.e., pre-existent life gave rise to new life.

Answer

Yes, a natural disaster can be the cause for extinction of species. As new species evolve to fit ever changing ecological niches, older species fade away. But, the rate of extincition is far from constant.

In last 500 million years, 50 - 90 % or more of all species on earth have disappeared in a geological blink of the eye. Many times, these mass extinctions had been the consequence of a natural disaster.

The most studied mass extinction between the Cretaceous and Palaeocene periods about 65 million years ago, killed off the dinosaurs and made room for mammals to rapidly diversify and evolve. The cause is suspected to be volcanic eruptions and impact of large asteroids or comets striking the earth.

Answer

Nascent oxygen is very reactive and can react with different biomolecules. Nascent oxygen is a permanent oxidising agent. It is highly reactive and can react readily with different kind of molecules including DNA, proteins present in the cells of aerobic life forms.

It is thus, considered toxic if it reacts with DNA, it can lead to mutations and defective proteins, both structural and functional. Similarly if it reacts with proteins and enzymes, they are degraded and many metabolic pathways may hence be impaired.

Answer

The creation and presence of variations is directionless in regard that they occur randomly and spontaneously. The variations which are helpful in the adaptations of an organism towards its surroundings would be passed on to next generations

Natural selection is the most critical evolutionary process, which can be considered directional as it leads to only one path that is selection and perpetuation of better adapted individuals. Natural selection leads to survival of the fittest and disappearance of all those organisms which do not all fit in the preveling environmental conditions.

Thinking Process

The peppered moths were initially white coloured, then black coloured due to industrialisation. In recent years, the light coloured moths are increasing in population again.

Answer

During the last century in the industrial regions of England, a light coloured peppered moth Biston betularia was found on the bark of trees. The tree bark was covered by whitish lichens, so light coloured moths escaped unnoticed from predatory birds.

After industrialisation, barks got covered by smoke, so the white moths were selectively picked up by birds. However, the black coloured moths escaped unnoticed against a dark background and became abundant.

However, in recent years, reduced industrial pollution has led to the growth of lichens again and thus, the population of light coloured moths is again increasing.

This evolutionary story of moths in England, thus reveals, that ’evolution is apparently reversible

Answer

Evolution helps us to understand the history of life. We can view evolution as a pattern of evolutionary change and as a process as well.

The world we see, all the inanimate and animate, is only the success stories of evolution. When we describe the story of this world, we describe evolution as a process.

On the other hand, when we describe the story of life an earth, we treat evolution as a consequence of a process called natural selection. Natural selection is the outcome of favourable variations among organisms and environmental conditions.

Thus, we are still not very clear whether to regard evolution and natural selection as processes or end result of processes.

Answer

Factors affecting allele frequency in populations are as described below

(i) Mutations These are sudden heritable changes which are supposed to be the primary source of genetic variation. They are of following two types

(a) Chromosomal Mutations They arise due to changes in chromosome number and changes in structure.

(b) Gene Mutations These are changes in gene structure and expression due to addition, deletion, substitution or inversion of nucleotides.

(ii) **Non-random Mating **Repeated mating between individuals of certain selected traits changes the gene frequency, e.g., selection of more brightly coloured male bird by a female bird may increase the gene frequency of bright colour in the next generation.

(iii) Gene Flow (Gene Migration) It is the movement of alleles into and out of a gene pool. Breeding of immigrants with the host population adds new alleles to the gene pool of the host population.

Answer

Yes, we agree. As the gene flow occurs through geographical barriers over generations, by studying specific allelic frequencies in various populations of the world, we can predict the human migratory patterns in pre-historic and historic era.

There have been projects undertaken such as human genographics project. Which uses data from studies on specific genes/chromosomes/mitochondrial DNA to trace the evolutionary history and migratory patterns of humans.

Answer

The meaning of the given words are as given below

Race It is a classification system used to categorise humans into large and distinct populations or groups by anatomical, cultural, linguistic, geographical, historical and for relegious relationship.

Breed It is a specific group of domestic animals or plants having homogenous appearance, homogenous behaviour and other characteristics that distinguish it from other animals or plants of the same species and that were arrived at through selective breeding.

Cultivar It is a plant or grouping of plants selected for desirable characteristics that can be maintained by propogation. ‘Cultivar’ stands for ‘cultivated variety’.

Variety A variety arises naturally in the plant kingdom and plant grown from its seeds will typically come out true to type.

Thinking Process

Those individuals which survice and reproduce in their respective environment are called fit.

Answer

In the struggle for existence, the individuals which have more favourable variations will enjoy a competitive advantage over others which have less favourable or unfavourable variations.

They are considered fit and thus, will survive and reproduce. Such individuals produce more progeny (with more fit individuals) than others who are less adapted in that environment.

Answer

Characteristic criteria for designating a Mendelian population are

(i) Population must be sufficiently large.

(ii) Population must have potentialities for free flow of genetic material among individuals, through sexual reproduction.

(iii) Migration should either be nil or negligible.

Answer

The movement of individuals from one place to another is called migration. It can be the movement of individuals to a different populations (i.e., emigration) or movement of individual into a particular population (i.e., cmmigration) Migration may bring in more such alleles, that bestow upon the individuals, such adaptations or traits which are selected by nature. Thus, enhancing the effect of selection.

Similarly, emigration may lead to removal of such alleles that confer better adaptations. Immigration may also bring in those alleles which confer the traits that are not selected by nature, i.e., blurr the effects of selection.

Hence, it is justifiable to say that ‘Migration may enhance or blurr the effects of selection.’

Answer

Hardy-Weinberg Principle states that the sum of allelic frequencies in a population is stable and is constant from generation to generation, i.e., the gene pool (total genes and their alleles in a population remains constant. This is called genetic equilibrium. The sum total of all the allelic frequencies is

Five factors that influence these values are

(i) Gene Migration or Gene Flow When migration of a section of population to another place occurs, gene frequencies change in the original as well as in the new population. New genes/alleles are added to the new population and these are lost from the old population. There would be gene flow if this gene migration, happens multiple times.

(ii) Genetic Drift It refers to the elimination of the genes of certain traits when a section of population migrates or dies of natural calamity. It is an evolutionary force operating in small populations whereby gene frequency changes by chance leadings to loss of some genes or gain of others irrespective of their selective advantages or disadvantages.

(iii) Mutation The sudden heritable change which is directionless in gene is called mutation. It alters the genetic frequency or genetic make up of an individual.

(iv) Genetic Recombination This phenomenon occurs during gamete formation when chromosomes pass from parents to offsprings which show new combination of characteristics.

(v) Natural Selection It is a phenomenon by which some members of population having traits that enable them to grow and reproduce at higher rater are favoured. Hence, they leave more surviving offspring in the next generation than others.

Answer

Divergent evolution is the evolution of a number of different forms of animals or plants froms of a common ancestral form. The driving force behind, it is adaptations to newly involved habitat and the prevailing environmental conditions there. As the original population increases in size, it spreads out from its centre of origin to exploit new habitas and food resources.

In time this results in a number of populations each adapted to its particular habitat, eventually these populations will differ from each other sufficiently to become new species.

A good example of this process is the evolution of the Australian marsupials into species adapted as carnivores, herbivores, burrowers, fliers, etc. Another example is that of peritadactyl limb in mammals.

The flipper of a seal, wing of a bat, forelimb of a male, front legs of horse and the arm of a man perform different functions, but exhibit the same structural plan including same pentadactyl pattern of bones.

Thinking Process

Prior to industrialisation, the light coloured moths were prevalent and well adapted to lichen covered trunks of trees.

Answer

In the population of pepper moth two variants exist the dark and the light coloured. Before industrialisation, the light coloured moths were prevalent because they blended well with the lichen covered bark of the trees.

The predators were unable to spot them and hence, their population were more in number. With industrialisation, the barks got covered with soot. The growth of lichens reduced, the light coloured moths were thus, spotted by the predators and their number decreased.

However, the black variants were camouflased better on soot covered barks and their number increased drastically.

If the industries were removed, the population of black moths would have declined because as stated before, they would not be able to camouflage against a light background (no black soot). Also the growth of lichens would increase. Therefore, the dark variants would be spotted better by predators and be eaten more frequently.

Answer

Key concepts of Darwin’s theory of evolution are as follows

(i) Over Production Living beings have an innate ability of producing own kind for the continuity of race. It has been observed that more individuals of each kind are produced than could possibly survive.

(ii) Struggle for Existence Individuals multiply in geometric ratio, whereas space and food remain almost limited.

(iii) Variations Members of a population vary is size, form and other characteristics even though they look superficially similar, no two individuals are alike. These variations are gradual and those with adaptive value are passed on to next generation.

(iv) Survival of the Fittest and Natural Selection During struggle for existence only those individuals could survive which exhibit beneficial variations and adapt better to changing environment. This is known as natural selection.

(v) Origin of Species Natural Selection results in modification of traits within a lineage, which over a period of long time can bring about evolution of original species into new one.

Answer

This phenomenon indicated in the question is convergent evolution where by organisms, not closely related, evolve similar traits independently as a result of adaptation to similar environment. e.g.,

(i) Streamlined shape of sharks and dolphins. The former is a fish, while dolphin is a mammal, but both of them depend on swift movement through the water, so a streamlined shape is essential. Thus, it is the similar habitat that resulted in selection of similar adaptive features in different groups of organisms, but toward the same function.

(ii) Spines (modified leaves) and thorns (modified stems), both look similar and provide protection to the plant, but the plants to which they belong are distantly related.

Answer

New research suggests that despite modern technology and industrialisation, ‘humans continue to evolve’. In the last 10,000 years or so, the pace of our evolution has speeded up 100 times creating more mutations in our genes and hence, greater natural selection.

Some clues that show humans are evolving are

(i) Lactose Tolerance Historically the gene that regulated human’s ability to digest lactose was shut down as infants are weaned off of their mother’s breast milk. However, adult human in regions of Africa and Northern Europe developed the ability to tolerate lactose in their diets as recent as 5,000 or 6,000 years ago due to mutations.

(ii) Wisdom Teeth Our ancestors had much bigger jaws than we do to lactose their eating habits. Today our jaws are much smaller and wisdom teeth are often impacted estimates say that they will disappear in the coming population.

Answer

Yes, had Darwin been aware of** Mendel’s** work, he would have been able to explain the origin of variations. Darwins observation of different forms of an individual in a population could be related to the presence of different forms of alleles of a gene.

The gene express as the most adaptive traits are selected naturally and become more abundant than those that are expressed as less adaptive traits.

Over the time, the accumulation of these traits might change the species to an extent that it develops into a new one and adapted to the specific environment.